How real software companies built it, with sources.

Marketplace for stays and experiences · United States

How Airbnb grew from a Rails monolith into services on Kubernetes

Airbnb started as a single Ruby on Rails app and, as the engineering team grew past a few hundred people, split it into Java services. Today it runs on AWS and Kubernetes, with a React and TypeScript web app, native iOS and Android apps, and data tools it built and open sourced, like Airflow and Superset.

Project management and email software (Basecamp and HEY) · United States

How 37signals runs Basecamp and HEY on Rails and its own servers

37signals makes Basecamp and the HEY email service with a small team, and it is the company behind Ruby on Rails. Its stack is Rails with Hotwire and MySQL, deployed with its own tool, Kamal, onto servers it owns, after leaving AWS between 2023 and 2025.

Scheduling infrastructure · United States

How Cal.com built scheduling in the open, then closed it

Cal.com is a scheduling platform and API that companies use to let people book time with them. For five years its code was public: a TypeScript monorepo with Next.js, tRPC, Prisma and Postgres, plus a NestJS API, until it moved production to a private repository in 2026.

Online ERP for small businesses and accountants · Brazil

How Conta Azul runs a small business ERP on AWS

Conta Azul is an online ERP that handles finances, sales and invoicing for Brazilian small businesses and their accountants. It runs on AWS, pairs a Java legacy with newer Go services, and serves thousands of per-customer ML models through Amazon SageMaker.

Secured lending and consumer credit · Brazil

How Creditas traded Ruby for Kotlin and moved to Kubernetes on AWS

Creditas offers loans backed by homes, cars and payroll in Brazil. It started on a Ruby monolith, moved new services to Kotlin and Spring Boot, runs them on Kubernetes in AWS, and now uses AI agents for maintenance and design system work.

Voice, video and text chat for communities · United States

How Discord handles trillions of messages with Elixir, Python and Rust

Discord is where millions of communities talk by text, voice and video. Its stack pairs Elixir for real-time connections with a Python API monolith, and over the years it has moved hot paths to Rust and storage from MongoDB to Cassandra to ScyllaDB.

Open source e-signature · United States

How Documenso built an open source DocuSign alternative

Documenso is an open source document signing platform that anyone can self-host or use as a cloud service. It runs on a TypeScript monorepo with React Router, Hono, tRPC, Prisma and PostgreSQL, and the team wrote its own PDF library to handle digital signatures.

Open source link management and attribution · United States

How Dub serves fast redirects and click analytics on a serverless stack

Dub is an open source platform for short links and link attribution, used by teams like Twilio, Vercel and Raycast. Its stack is built almost entirely from managed services: Next.js on Vercel for the app and redirects, Redis to cache links, MySQL on PlanetScale for core data and Tinybird for click analytics.

Language learning app · United States

How Duolingo scaled from a Python backend to 500 services on AWS

Duolingo teaches languages, math and music to a huge audience through native mobile apps and the web. Its backend started in Python and grew into more than 500 services on AWS written in Python, Kotlin and Java, while the apps are native Swift and Kotlin and use AI from OpenAI.

Collaborative design tool · United States

How Figma built a game-engine-grade design tool in the browser

Figma is a design tool where whole teams edit the same file live in the browser. Its canvas is C++ compiled to WebAssembly with a React and TypeScript UI around it, backed by a Rust multiplayer server, a Ruby monolith and a heavily sharded Postgres fleet on AWS.

Publishing platform for newsletters and paid memberships · SG

How Ghost built an open source publishing platform on Node.js

Ghost is an open source publishing platform run by a nonprofit foundation, used for blogs, newsletters and paid memberships. Its core is a Node.js JSON API with MySQL, a separate admin app now being rebuilt in React, and outside services like Stripe, Mailgun and Tinybird for payments, email and analytics.

DevSecOps platform for code, CI/CD and security · United States

How GitLab runs a giant Rails monolith in the open

GitLab is an open-core platform that covers source control, CI/CD and security in one app, and GitLab.com is the largest install of it. The stack is a deliberately boring Ruby on Rails monolith with PostgreSQL, Redis and Sidekiq, plus Go services for the hot paths, running on Google Cloud and Kubernetes.

Platform for selling digital products and courses · Brazil

How Hotmart built its creator platform on AWS and Java

Hotmart lets creators sell and deliver courses and other digital products, with checkout, members area and payments in one place. It has run on AWS since it was founded, with Java services on Kubernetes and, more recently, an AI tutor built on Amazon Bedrock.

Food and grocery delivery · Brazil

How iFood runs Latin America's biggest delivery app on Kotlin, events and data

iFood connects restaurants, markets and couriers to millions of customers, at about 100 million orders a month. Its backend is made of Kotlin and Java microservices on AWS and Kubernetes, talking through Kafka and events, with Databricks and SageMaker behind the data and the hundreds of ML models.

Project management for software teams · United States

How Linear built a fast issue tracker

Linear is an issue tracker and project planning tool for software teams, known for feeling instant. Under the hood it runs TypeScript end to end, with its own sync engine keeping data on the client and a single Postgres database on Google Cloud.

Connected workspace for docs, wikis and projects · United States

How Notion scaled Postgres and its data stack

Notion is a workspace where teams write docs, build wikis and manage projects, all made of blocks. Its product runs on React, TypeScript and Node.js over a sharded Postgres fleet on AWS, with a Kafka, Hudi and Spark data lake built to keep up with billions of blocks.

Digital bank · Brazil

How Nubank built a bank on Clojure and Datomic

Nubank is the digital bank that started with a credit card in Brazil and now serves millions of customers across Latin America. From day one it bet on Clojure, the Datomic database and Kafka on AWS, later moved everything to Kubernetes and went on to buy the company behind Clojure.

E-commerce platform for small retailers · Brazil

How Olist built a marketplace hub on Python, Django and queues

Olist helps small Brazilian merchants sell on the big marketplaces and run their stores. Its stack is Python and Django REST Framework end to end, with more than a hundred microservices talking through Amazon SQS queues.

Digital wallet and bank · Brazil

How PicPay scaled a payments super app on AWS

PicPay started as a peer-to-peer payments wallet and grew into a full digital bank. It was built on AWS from early on, with apps on Kubernetes in EKS, Kafka on MSK, and a data platform that moved to Databricks.

Privacy-friendly web analytics · Estonia

How Plausible built a lightweight Google Analytics alternative

Plausible is an open source, cookie-free analytics tool run by a tiny bootstrapped team in the EU. Its stack is an Elixir and Phoenix monolith, with PostgreSQL for app data and ClickHouse for the stats, running on servers in Germany.

Product analytics and developer tools · United States

How PostHog built open source product analytics that scales

PostHog is an open source suite for product analytics, session replay, feature flags and experiments. Its stack is a Django and React app on top of ClickHouse, with Rust services and Kafka taking care of the firehose of incoming events.

Home rental and sales marketplace · Brazil

How QuintoAndar built a housing marketplace on React, Flutter and Databricks

QuintoAndar connects owners, tenants, buyers and agents to rent and sell homes in Brazil. Its stack pairs a React web app and a Flutter mobile app with a monolith being split into services and a heavy data and ML platform on Databricks and AWS.

Productivity launcher for Mac and Windows · United Kingdom

How Raycast built a native launcher that runs on Mac and Windows

Raycast is a keyboard launcher with extensions, AI chat and file search. It started as a pure Swift and AppKit Mac app, and Raycast 2.0 became a hybrid: thin native shells, a shared React UI in system web views, a Node.js core and Rust where speed matters.

Marketing automation and CRM for small businesses · Brazil

How RD Station grew a Rails app from Heroku to a multi-cloud platform

RD Station, founded as Resultados Digitais in Florianópolis, makes marketing automation, CRM and customer service software and has been part of TOTVS since 2021. It started as a Ruby on Rails app on Heroku and today runs Rails and Python services on Kubernetes across Google Cloud and AWS.

Email API for developers · United States

How Resend built an email API on TypeScript and Supabase

Resend is an email API that lets developers send transactional and marketing email with a few lines of code. It grew out of the open-source React Email project and runs on TypeScript, Node.js and Go on AWS, with Postgres and auth from Supabase.

E-commerce platform · Canada

How Shopify scaled one of the largest Rails apps in the world

Shopify runs online and in-person stores for millions of merchants. Its core is still a Ruby on Rails monolith, kept modular and split into isolated pods with sharded MySQL, running on Kubernetes in Google Cloud, with React, GraphQL and React Native on the client side.

Team messaging and collaboration · United States

How Slack grew from a PHP app into a cellular platform on AWS

Slack is a messaging app for work, used by teams of every size. Its backend is a Hack monolith on HHVM with Java real-time servers, MySQL scaled through Vitess and a Kubernetes platform on AWS, while the desktop client is React and TypeScript inside Electron.

Payments, banking and credit for small businesses · Brazil

How Stone runs payments and banking on C#, Go and three clouds

Stone sells card machines, a digital business account and credit to Brazilian merchants. Its engineering splits by business line, with C# and .NET in credit, Go in banking, Kotlin Multiplatform on mobile, and infrastructure spread across AWS, Google Cloud and Azure.

Postgres development platform · United States

How Supabase assembled a backend from open-source tools

Supabase gives developers a Postgres database with auth, APIs, file storage, realtime and edge functions around it. Rather than writing everything from scratch, it combines existing open-source tools in several languages and builds only what is missing, all hosted on AWS.

Cloud platform for web apps · United States

How Vercel builds Vercel on its own tools

Vercel is a cloud platform for deploying web apps and the company behind Next.js. Its own site and dashboard run on Next.js and Turborepo, while the platform underneath mixes AWS Lambda, a Rust core, Go at the edge and a Kafka and ClickHouse data pipeline.